The invention relates to a pointer instrument having a pointer shaft that deflects an essentially transparent pointer, having an illuminating means that radiates directly into a flag of the pointer, having a carrier which is fastened to the pointer shaft, holds the pointer and has contact surfaces for making contact with the illuminating means, having a connecting sleeve that has connecting contacts for a connection to a power supply, and having conductors to connect the connecting contacts and the contact surfaces.
Such a pointer instrument, in which the illuminating means, together with the pointer, is fastened to the carrier and radiates directly into the pointer flag, is known. In this case, the carrier has an electrically conductive inner body that is connected to one pole of the illuminating means, and an electrically conductive outer body that is connected to the other pole of the illuminating means, the inner body and outer body being separated from each other by insulation. The connecting sleeve has an inner body, which is connected to the pointer shaft, and an outer body, these being separated from each other by an insulation layer and each having connecting contacts. The power is supplied to the connecting contacts of the connecting sleeve through two spiral spring strips, which are constructed in the manner of a sandwich with the interposition of an insulating layer. The inner body and the outer body of the connecting sleeve are each connected to one of the spring strips. The electrical connection between the carrier and the connecting sleeve is achieved via the pointer shaft and via a compression spring arranged between the outer bodies of the carrier and of the connecting sleeve.
The disadvantage with such a pointer instrument is that the connecting sleeve and the carrier consist of very many components, which are complicated to produce and to assemble. Furthermore, there is an unnecessarily large number of contact points between the power supply and the illuminating means, and these impair the functional reliability of the pointer instrument. Since the compression spring forces the carrier and the connecting sleeve away from each other, these must be connected particularly firmly to the pointer shaft, in order to ensure the permanent supply of electric power to the illuminating means.
The invention is based on the problem of configuring a pointer instrument of the type mentioned at the beginning in such a way that it is simply constructed and has a particularly high functional reliability.
According to the invention, this problem is solved by the connecting sleeve forming the carrier at its end facing the pointer, by the conductors running continuously from the connecting contacts to the contact surfaces, and by the connecting sleeve being produced from a nonconductive plastic and the conductors, the contact surfaces and the connecting contacts being produced from conductive plastic.
This configuration means that the novel pointer instrument is particularly simply constructed. Power supply to the illuminating means is thus no longer carried out, as in the case of the known pointer instrument, via the pointer shaft, which is generally produced from metal, or via the compression spring, but rather via the conductors which run continuously from the connecting contacts to the contact surfaces. By this means, the number of contact points is kept as small as possible, which increases the functional reliability of the novel pointer instrument. The use of electrically conductive plastic likewise contributes to the functional reliability of the pointer instrument, since electrically conductive plastic is not permanently covered by an electrically insulating oxide layer, as is the case with metal, for example. A further advantage of the connecting sleeve is that it has a particularly low weight, so that it is scarcely able to hamper the movement of the pointer as a result of its mass moment of inertia. The connecting sleeve can be produced, for example, completely by plastic injection molding, so that subsequent assembly is dispensed with. By this means, the connecting sleeve is configured particularly cost-effectively.
The novel pointer instrument can be assembled very simply if the connecting contacts are designed as plug-in contacts. In this way, the connecting sleeve is simply plugged onto the pointer shaft for the purpose of assembly.
The connecting sleeve is configured in a particularly space-saving manner and at the same time has a good mechanical connection to the pointer if, according to an advantageous development of the invention, it is of mushroom-like configuration and holds the pointer with its cap region.
The illuminating means could be, for example, an incandescent filament. However, the illuminating means has a particularly low energy consumption and is able to illuminate the pointer well if it is an LED chip. Furthermore, such an LED chip has a particularly long service life, as compared with other illuminating means, so that exchange of the illuminating means during the service life of the pointer instrument only has to be carried out infrequently, if at all.
The pointer flag is particularly well illuminated, without the outlay in terms of assembly for the pointer instrument being increased, if, according to an advantageous development of the invention, reflectors of electrically conductive plastic are arranged at that end of the connecting sleeve which faces the pointer, and if at least two reflectors are designed as contact surfaces for making contact with the illuminating means.
The illuminating means can be exchanged easily if, according to another advantageous development of the invention, the connecting sleeve has, at its end facing the pointer, a mount which is upright, of C-shaped cross section, open at the top and in the direction of the pointer flag and has contact surfaces arranged in it, and if the illuminating means is arranged on a circuit board which is designed to be pushed into the mount. By this means, the connecting sleeve may be produced as a standard component for different pointer instruments which are intended to have pointers that have different brightnesses or various colors.
In order to set the brightness, in particular of light-emitting diodes, the latter are often preceded by balancing resistors. These balancing resistors are configured particularly simply if a planar balancing resistor is applied to the surface of the connecting sleeve. Such a planar balancing resistor may be removed, for example using a laser beam, until the desired resistance value and hence the desired brightness of the illuminating means has been reached.
It is often the case that the pointer of the novel pointer instrument pivots only over a range of 120xc2x0 to 270xc2x0. In this case, the electrical connection between the connecting sleeve and the power supply is particularly simply configured, according to another advantageous development of the invention, if the connecting sleeve has sinuous wires of conductive plastic that are injection molded on. By virtue of the sinuous shape, the wires can be bent and stretched easily, by which means the movement of the pointer shaft is not impeded.
According to another advantageous development of the invention, contact is made between the connecting sleeve and the power supply in a particularly space-saving manner if a bifilar helical spring with a low spring force is soldered onto the connecting contacts of the connecting sleeve.
In the case of pointers that pivot over a particularly large range, contact may be made with the connecting sleeve, as in the known pointer instrument, using spiral springs, which would then have to be soldered or plugged onto the connecting sleeve. These spiral springs either could have a particularly low spring force or could be arranged in pairs and in opposite directions. However, contact is made between the connecting sleeve and the power supply particularly simply in design terms if the pointer instrument has a flexible, spiral sheet with conductor tracks printed on it, and the conductor tracks are soldered or clamped to the power supply and to the connecting contacts of the connecting sleeve. Such a sheet can be produced particularly cost-effectively, and has a barely perceptible spring force.
According to another advantageous development of the invention, contact is made between the connecting sleeve and the power supply particularly simply if a strip of a heat-seal sheet with conductor tracks printed on it is arranged between the connecting sleeve and the power supply, the heat-seal sheet being swept in a U shape between the power supply and the connecting sleeve when the pointer is in a basic position. By the heat-seal sheet being heated and pressed simultaneously onto the connecting contacts of the connecting sleeve and of the power supply, this sheet is fastened and, at the same time, contact is made with it.
According to another advantageous development of the invention, the connecting sleeve is quick to assemble and disassemble if the connecting sleeve has slip rings running around its circumference at different heights, against which prestressed contact springs rest, these springs being connected to the power supply of the pointer instrument. Since in this case the number of slip rings is limited only by the dimensions of the connecting sleeve, it is possible here to insert a plurality of illuminating means very easily and to activate them differently. For example, a plurality of illuminating means of different colors can be inserted, and the pointer can, in different states, be illuminated in different colors.
The connecting sleeve has no mechanical connection to the power supply of the pointer instrument if the connecting sleeve has a first coil, which is located opposite a second coil of the pointer instrument, the second coil being designed to set up a magnetic field and to generate an electric current in the first coil. This configuration is particularly advantageous in the case of pointers which are intended to have the lowest possible inherent damping. Furthermore, in this case the risk of contamination of slip rings or of breakage of springs and sheets is ruled out.